China will start reclamation at the Scarborough Shoal in the South China Sea later this year and may add an airstrip to extend its air force’s reach over the contested waters, a military source and mainland maritime experts say.

A source close to the PLA Navy said Beijing would ramp up work to establish a new outpost 230km off the coast of the Philippines as the US and Manila drew their militaries closer together.

An upcoming ruling on territorial claims by the Permanent Court of Arbitration at The Hague, widely expected to go against China, would also accelerate the plan, the source said.

Manila wants the court to ­declare that Beijing’s claims must comply with the United Nations Convention on the Law of the Sea, and the decision could come next month or in June.

“Beijing will take action to carry out land reclamation at Huangyan Island within this year,” said the source, who ­requested anonymity, referring to the shoal.

“China should regain the initiative to do so because Washington is trying to contain Beijing by establishing a permanent military presence in the ­region.”

The US and the Philippines began joint patrols in the South China Sea in March, US ­defense chief Ash Carter revealed during his latest visit to the region. US forces will also have ­access to at least eight military bases in the Philippines, with two air bases in Pampanga, 330km from Scarborough Shoal.